Dual compression driver with single magnet

Embodiments relate to a dual compression driver with a single, shared magnet.

Dual compression drivers include two annular diaphragms, where the diaphragms either have the same profile and work in the same frequency range or have different profiles and radiate in different frequency bands. In addition to the two diaphragms, a dual compression driver includes two motor assemblies and two phasing plugs. The phasing plugs are positioned adjacent to each other and the diaphragms radiate through two acoustic chambers that have a mutual acoustic load (waveguide or horn). Accordingly, the time delay between two exits from the adjacent phasing plugs is very small (less than a quarter wavelength at the highest frequency) and therefore it does not create interference nor a combing effect in the audio frequency range.

Comparing a dual compression driver with a regular driver having a dome diaphragm and the same diameter of the voice coil, the moving mass of each diaphragm in the dual compression driver is lower because the mass is split between the two diaphragms. Advantageously, a lower moving mass extends the high-frequency range of the dual compression driver. Having two voice coils instead of one decreases the thermal compression and increases the dynamic range and the maximum SPL (sound pressure level), because the same level of the output acoustic signal is reached at a smaller displacement of each voice coil and each diaphragm. For the same reason, the distortion at low frequencies is smaller as well in dual compression drivers compared with regular drivers. However, the disadvantage of the dual compression driver is its high cost because of the necessity to use two motor assemblies with two expensive neodymium magnets.

In one or more embodiments, a dual compression driver includes a first driver assembly including a first annular diaphragm disposed about a central axis, and a first phasing plug disposed coaxially below the first annular diaphragm and including a first plurality of apertures extending therethrough. The dual compression driver further includes a second driver assembly including a second annular diaphragm disposed about the central axis, and a second phasing plug disposed coaxially above the second annular diaphragm and including a second plurality of apertures extending therethrough. A shared annular magnet is disposed between the first driver assembly and the second driver assembly. A back cover is mounted to the first phasing plug, wherein the back cover and the first phasing plug form a first acoustic pathway for acoustic signals from the first plurality of apertures. A front adapter is mounted to the second phasing plug and has a hollow conduit formed therein along the central axis defining a circular exit of the dual compression driver, wherein the front adapter and the second phasing plug form a second acoustic pathway for acoustic signals from the second plurality of apertures. Acoustic signals from the first plurality of apertures and acoustic signals from the second plurality of apertures merge and radiate through the hollow conduit to the circular exit.

In one or more embodiments, the first driver assembly includes a first top plate disposed coaxially above the first annular diaphragm, and the second driver assembly includes a second top plate disposed coaxially below the second annular diaphragm, the shared annular magnet disposed between the first top plate and the second top plate. In one or more embodiments, the first phasing plug has a first inner edge and the second phasing plug has a second inner edge, wherein the first inner edge and the second inner edge are adjacent to each other such that the first acoustic pathway and the second acoustic pathway converge. In one or more embodiments, an output side of the first phasing plug oriented away from the first annular diaphragm includes a first plurality of radial channels extending inwardly from the first plurality of apertures to the first inner edge, and an output side of the second phasing plug oriented away from the second annular diaphragm includes a second plurality of radial channels extending inwardly from the second plurality of apertures to the second inner edge.

In one or more embodiments, the first phasing plug and the second phasing plug each have an outer portion and an inner portion joined by an intermediate portion, wherein each outer portion is generally planar, wherein each intermediate portion has an inclined section and a flat section, and wherein each inner portion is generally sloped and terminates in the first inner edge of the first phasing plug and terminates in the second inner edge of the second phasing plug. In one or more embodiments, the inner portion of the first phasing plug extends through the first annular diaphragm and the inner portion of the second phasing plug extends through the second annular diaphragm. In one or more embodiments, the first plurality of apertures are formed in the intermediate portion of the first phasing plug, and the second plurality of apertures are formed in the intermediate portion of the second phasing plug.

In one or more embodiments, the first annular diaphragm and the second annular diaphragm each have an external portion and an internal portion joined by a middle portion, wherein each external portion and each internal portion are generally planar and each first middle portion is generally sloped such that a plane of each internal portion is offset from a plane of each external portion. In one or more embodiments, the middle portion of the first annular diaphragm is aligned with the inclined section of the first phasing plug, and the middle portion of the second annular diaphragm is aligned with the inclined section of the second phasing plug. In one or more embodiments, each middle portion includes a step section configured for attaching a first voice coil to the first annular diaphragm and a second voice coil to the second annular diaphragm.

In one or more embodiments, the first plurality of apertures and the second plurality of apertures are each arranged generally circumferentially about the central axis. In one or more embodiments, the back cover has a peripheral portion and a central portion, the central portion including a hub portion extending at least partially into the hollow conduit. In one or more embodiments, a first compression chamber is defined between an input side of the first phasing plug and the first annular diaphragm, and a second compression chamber is defined between an input side of the second phasing plug and the second annular diaphragm, the first plurality of apertures forming an exit to the first compression chamber and the second plurality of apertures forming an exit to the second compression chamber.

In one or more embodiments, a dual compression driver includes a first driver assembly including a first annular diaphragm disposed about a central axis, a first phasing plug disposed coaxially below the first annular diaphragm and having a first inner edge, and a first top plate disposed coaxially above the first annular diaphragm, the first phasing plug including a first plurality of apertures extending therethrough. The dual compression driver further includes a second driver assembly including a second annular diaphragm disposed about the central axis, a second phasing plug disposed coaxially above the second annular diaphragm and having a second inner edge, and a second top plate disposed coaxially below the second annular diaphragm, the second phasing plug including a second plurality of apertures extending therethrough. A shared annular magnet is disposed between the first top plate and the second top plate. A back cover is mounted to the first phasing plug, wherein the back cover and the first phasing plug form a first acoustic pathway for acoustic signals from the first plurality of apertures. A front adapter is mounted to the second phasing plug and has a hollow conduit formed therein along the central axis and defining a circular exit of the dual compression driver, wherein the front adapter and the second phasing plug form a second acoustic pathway for acoustic signals from the second plurality of apertures. The first inner edge and the second inner edge are adjacent to each other such that the first acoustic pathway and the second acoustic pathway converge at a central bore of the dual compression driver, such that acoustic signals from the first plurality of apertures and acoustic signals from the second plurality of apertures radiate inward toward the central bore then merge and radiate through the hollow conduit to the circular exit.

In one or more embodiments, a dual compression driver includes a first driver assembly including a first annular diaphragm disposed about a central axis, and a first phasing plug disposed coaxially below the first annular diaphragm, the first phasing plug including an input side oriented toward the first annular diaphragm and an output side oriented away from the first annular diaphragm, the first phasing plug including a first plurality of apertures extending therethrough. The dual compression includes a second driver assembly including a second annular diaphragm disposed about the central axis, and a second phasing plug disposed coaxially above the second annular diaphragm, the second phasing plug including an input side oriented toward the second annular diaphragm and an output side oriented away from the second annular diaphragm, the second phasing plug including a second plurality of apertures extending therethrough. A shared annular magnet is disposed between the first driver assembly and the second driver assembly. A back cover is mounted to the first phasing plug, wherein an inner surface of the back cover and the output side of the first phasing plug form a first acoustic pathway for acoustic signals from the first plurality of apertures. A front adapter is mounted to the second phasing plug and having a hollow conduit formed therein along the central axis, the hollow conduit having a bottom end adjacent to the second phasing plug and a top end defining a circular exit of the dual compression driver, wherein an inner surface of the front adapter and the output side of the second phasing plug form a second acoustic pathway for acoustic signals from the second plurality of apertures. Acoustic signals from the first plurality of apertures and acoustic signals from the second plurality of apertures merge and radiate through the hollow conduit to the circular exit.

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

It is understood that directional identifiers such as, but not limited to, top, bottom, above, below, upper, lower, upwardly and downwardly used herein for descriptive purposes are not intended to be limiting, and are simply used to provide an exemplary environment for the components of the dual compression driver as disclosed herein. Any directional terms as used herein are merely to indicate the relative placement of various components of the dual compression driver and are not intended to limit components to any particular orientation in space.

According to one or more embodiments, a dual compression driver is disclosed herein that uses a single magnet shared between two driver assemblies. This design is scalable and helps to significantly decrease the cost of the dual compression driver by only requiring one magnet. In the single magnet configuration as disclosed herein, the phasing plugs and their corresponding diaphragms are not positioned against each other as they would be in a typical dual driver, such that the diaphragms become separated not only by the thicknesses of the phasing plugs, but by the thickness of the shared magnet and the two top plates as well. In order to prevent a delay between the phasing plug exits as well as to prevent the generation of any unwanted combing effect at high frequencies, embodiments of the dual compression driver disclosed herein minimize this time delay via a specialized configuration of the diaphragms and the phasing plugs as described below.

1 3 FIGS.- 100 102 104 102 104 100 106 With reference first to, a dual compression driveris disclosed herein including a first or rear driver assemblyand a second or front driver assemblywhich may be utilized in a transducer or loudspeaker. The first driver assemblyand the second driver assemblymay be configured to operate in the same frequency range or in different frequency ranges. The various components of the dual compression drivermay be disposed generally about a central axis.

3 FIG. 3 5 FIGS.- 102 108 106 104 110 106 108 110 108 110 10 108 110 112 114 116 116 112 114 112 114 100 112 114 116 114 112 As shown in the cross-sectional view of, the first driver assemblyincludes a first annular diaphragmdisposed about the central axis, and the second driver assemblyincludes a second annular diaphragmdisposed about the central axis. In one or more embodiments, the first annular diaphragmand the second annular diaphragmmay be constructed from a polymer film. The first annular diaphragmand the second annular diaphragmare identical, but disposed with opposing orientations. As shown inand, the first annular diaphragmand the second annular diaphragmeach have an external portionand an internal portionjoined by a middle portion. In one or more embodiments, the middle portionmay include a coating to increase its stiffness or it may be constructed from a stiffer material compared with the external portionand the internal portion, such that the external portionand the internal portionmay act as flexible suspensions. Conventional annular diaphragms may include a V-shaped section between inner and outer, co-planar clamping portions. In contrast, according to one or more embodiments of the dual compression driverdisclosed herein, the external portionand the internal portionare each generally planar, and the middle portionis generally sloped such that a plane of the internal portionis offset from a plane of the external portion.

116 118 120 108 122 110 116 116 116 118 112 114 116 116 112 114 118 116 116 118 116 116 108 110 3 FIG. 5 FIG. a b a b a b a b In one or more embodiments, the middle portionincludes a step sectionconfigured for attaching a first voice coilto the first annular diaphragmand a second voice coilto the second annular diaphragm(). With reference to, while each segmentandof the middle portion(on either side of the step section) is depicted herein as having the same angle with respect to the external portionand the internal portionand with respect to each other, these segments,instead may have different angles with respect to the external portionand the internal portionand with respect to each other. In the latter instance, the step sectionmay be biased inward such that an internal angle between the segments,is obtuse, or the step sectionmay be biased outward such that the internal angle between the segments,is acute. Either of these configurations may provide added flexibility in controlling the mechanical behavior of the first annular diaphragmand the second annular diaphragm.

3 6 10 FIGS.and- 102 124 108 104 126 110 124 126 124 128 108 130 108 126 128 110 130 110 124 132 128 130 126 134 128 130 Turning now to, the first driver assemblyincludes a first phasing plugis disposed coaxially below the first annular diaphragm, and the second driver assemblyincludes a second phasing plugdisposed coaxially above the second annular diaphragm. The first phasing plugand the second phasing plugare identical, but disposed with opposite orientations. The first phasing plugand includes an input sideoriented toward the first annular diaphragmand an output sideoriented away from the first annular diaphragm. Correspondingly, the second phasing plugincludes an input sideoriented toward the second annular diaphragmand an output sideoriented away from the second annular diaphragm. The first phasing plugincludes a first plurality of aperturesextending therethrough from the input sideto the output side, and the second phasing plugincludes a second plurality of aperturesextending therethrough from the input sideto the output side.

124 126 108 110 124 126 136 138 140 136 106 140 142 144 138 124 146 138 126 148 130 124 150 132 146 130 126 152 134 148 132 134 150 152 132 140 124 134 140 126 The first phasing plugand the second phasing plugmay be configured to correspond to the shape of the first annular diaphragmand second annular diaphragm, respectively. The first phasing plugand the second phasing plugeach have an outer portionand an inner portionjoined by an intermediate portion. In one or more embodiments, each outer portionmay be generally planar and lie in a plane orthogonal to the central axis. Each intermediate portionhas an inclined sectionand a flat section. The inner portionof the first phasing plugis generally sloped and terminates in a first inner edgeand the inner portionof the second phasing plugis generally sloped and terminates in a second inner edge. The output sideof the first phasing plugincludes a first plurality of radial channelsextending inwardly from the first plurality of aperturesto the first inner edge, and the output sideof the second phasing plugincludes a second plurality of radial channelsextending inwardly from the second plurality of aperturesto the second inner edge. Each of the first and second pluralities of apertures,is therefore acoustically connected to a corresponding one of the first and second pluralities of radial channels,. In one or more embodiments, the first plurality of aperturesare formed in the intermediate portionof the first phasing plug, and the second plurality of aperturesare formed in the intermediate portionof the second phasing plug.

3 FIG. 154 128 124 108 132 154 156 128 126 110 134 156 108 110 154 156 154 156 In a compression driver, the diaphragm is loaded by a compression chamber, which is a thin layer of air separating the diaphragm from the phasing plug. In the embodiments disclosed herein, and with reference to, a first compression chamberis defined between the input sideof the first phasing plugand the first annular diaphragm, where the first plurality of aperturesform an exit to the first compression chamber. A second compression chamberis defined between the input sideof the second phasing plugand the second annular diaphragm, where the second plurality of aperturesform an exit to the second compression chamber. The volume of air entrapped in the compression chamber is characterized by an acoustical compliance which is proportional to the volume of compression chamber. In practice, the height of the compression chamber may be quite small (e.g., approximately 0.5 mm or less) such that the volume of the compression chamber is also small. The small radial dimension of the first annular diaphragmand the second annular diaphragmcorresponds to the small radial dimensions of the matching compression chamber,, which shifts undesirable air resonances (cross-modes) in the compression chamber,to higher frequencies, sometimes above the audio range.

124 126 116 108 142 124 116 110 142 126 138 124 108 138 126 110 108 110 124 126 124 126 150 152 146 148 124 126 3 10 FIGS.and The first phasing plugand the second phasing plugare directed radially towards each other at an angle. In one or more embodiments, the middle portionof the first annular diaphragmis aligned with the inclined sectionof the first phasing plug, and the middle portionof the second annular diaphragmis aligned with the inclined sectionof the second phasing plug. As best shown in, the inner portionof the first phasing plugis configured to extend through the first annular diaphragm, and the inner portionof the second phasing plugis configured to extend through the second annular diaphragm. The configuration of the first and second annular diaphragms,and the first and second phasing plugs,contributes to minimizing the distance between the radial exits of the first and second phasing plugs,(the first and second pluralities of radial channels,) at the first inner edgeand the second inner edge, such that the radial exits of the first and second phasing plugs,converge with a minimum axial distance between them.

3 FIG. 102 158 108 104 160 110 100 162 102 104 158 160 162 120 116 108 162 122 116 110 With reference to, the first driver assemblyincludes a first annular top platedisposed coaxially above the first annular diaphragm, and the second driver assemblyincludes a second annular top platedisposed coaxially below the second annular diaphragm. In one or more embodiments, the dual compression driverincludes a single, shared annular permanent magnetdisposed between the first driver assemblyand the second driver assembly, such as between the first top plateand the second top plate. The shared magnetprovides a permanent magnetic field for electrodynamic coupling with the first voice coilwhich produces movement of the flexible, middle portionof the first annular diaphragmto convert received electrical signals into acoustic signals (sound waves). The shared magnetalso provides a permanent magnetic field for electrodynamic coupling with the second voice coilwhich produces movement of the flexible, middle portionof the second annular diaphragmto convert received electrical signals into acoustic signals.

108 132 124 110 134 126 124 126 108 110 132 134 106 132 134 106 132 134 154 156 100 132 134 6 10 FIGS.- Acoustic signals created by the first annular diaphragmtravel through the first plurality of apertureswhich serve as an entrance to the first phasing plug, and acoustic signals created by the second annular diaphragmtravel through the second plurality of apertureswhich serve as an entrance to the second phasing plug. Accordingly, the area of the entrance to the first phasing plugand to the second phasing plugis significantly smaller than the area of the first annular diaphragmand the second annular diaphragm, respectively. As illustrated in, the first plurality of aperturesand the second plurality of aperturesmay each be arranged generally circumferentially about the central axis, generally forming a circle. In one or more embodiments, the first plurality of aperturesand the second plurality of apertureseach have a “zig-zag” or sawtooth type configuration arranged generally circumferentially about the central axisas shown. Such a meandering configuration of the apertures,helps to mitigate any adverse influence of diaphragm breakups on frequency response, and may have the effect of smearing the air resonances in the first and second compression chambers,so as to shape and improve the wavefront exiting the dual compression driver. However, the first plurality of aperturesand the second plurality of aperturesare not limited to the embodiments depicted herein and may include other suitable shapes and configurations.

3 14 FIGS.and 3 FIG. 102 164 108 158 104 166 110 160 168 164 170 166 164 166 172 174 172 176 178 178 164 116 108 178 166 116 110 With reference to, the first driver assemblymay also include a first annular pole piecedisposed coaxially above the first annular diaphragmand inset from the first top plate. Likewise, the second driver assemblymay also include a second annular pole piecedisposed coaxially below the second annular diaphragmand inset from the second top plate. As shown in, a top surfaceof the first pole pieceabuts a bottom surfaceof the second pole piece. The first pole pieceand the second pole piecemay each include an outboard portionhaving a greater thickness than an inboard portionthereof, wherein the outboard portionhas a recessed surfaceand an inclined surface. The inclined surfaceof the first pole piecemay be oriented toward the middle portionof the first annular diaphragm, and the inclined surfaceof the second pole piecemay be oriented toward the middle portionof the second annular diaphragm.

3 15 FIGS.and 100 180 182 162 184 164 166 176 186 188 164 190 188 166 186 112 108 164 124 190 112 110 166 126 102 104 192 106 100 As shown in, the dual compression drivermay further include an insert ringhaving an outer faceconfigured to abut the shared magnet, and an inner projectionconfigured to be disposed between the first pole pieceand the second pole pieceand received within each corresponding recessed surface. A first glue ringmay be disposed coaxially below an inner edgeof the first pole piece, and a second glue ringmay be disposed coaxially above an inner edgeof the second pole piece. The first glue ringmay secure and/or clamp the external portionof the first annular diaphragmto the first pole pieceand the first phasing plug, and the second glue ringmay secure and/or clamp the external portionof the second annular diaphragmto the second pole pieceand the second phasing plug. In general, components of the first driver assemblyand the second driver assemblymay be connected together by fasteners or adhesives. A central borecoaxial with the central axisis defined by the annular components of the dual compression driver.

1 3 11 12 FIGS.-and- 3 FIG. 194 124 196 198 198 196 198 200 192 200 200 192 202 106 204 194 130 124 206 132 102 As illustrated in, a back coveris mounted to the first phasing plugand has a peripheral portionand a central portion, wherein a plane of the central portionmay offset (e.g. upward) from a plane of the peripheral portion. In one or more embodiments, the central portionmay include a hub portionextending into the central bore, wherein the hub portionmay have an elongated, generally bullet-shaped profile. That is, a diameter of the hub portionis less than an inside diameter of the central bore, and may taper in the axial direction to a sharp or domed tiplocated on the central axis. As best shown in, an inner surfaceof the back coverand the output sideof the first phasing plugform a first acoustic pathwayfor acoustic signals from the first plurality of aperturesand the first driver assembly.

1 3 13 FIGS.-and 1 3 FIGS.- 3 FIG. 208 126 210 106 210 192 200 210 126 210 212 126 214 100 214 212 210 212 214 212 192 208 216 104 136 126 208 104 162 102 216 208 130 126 218 134 104 With reference to, in one or more embodiments a front adapteris mounted to the second phasing plugand includes a hollow conduitformed therein along the central axis, wherein the hollow conduitmay be considered as an extension of the central bore. In one or more embodiments, the hub portionmay extend at least partially through the hollow conduit, and may extend to an axial elevation above the second phasing plug. The hollow conduithas a bottom endadjacent to the second phasing plugand a top end which defines a circular exitof the dual compression driver. A diameter of the top end or circular exitmay be greater than a diameter of the bottom end, such that hollow conduittapers outwardly from the bottom endto the circular exit, wherein the diameter of the bottom endmay be substantially the same as a diameter of the central bore. The front adapterhas an inner surfacedisposed on or attached to the second driver assembly, such as the outer portionof the second phasing plug. As shown in, the front adaptermay substantially surround the second driver assemblyand the shared magnet, and possibly the first driver assemblyas well. As best shown in, the inner surfaceof the front adapterand the output sideof the second phasing plugtogether form a second acoustic pathwayfor acoustic signals from the second plurality of aperturesand the second driver assembly.

3 FIG. 146 124 148 126 206 218 192 132 206 134 218 192 210 208 214 100 132 134 150 152 206 218 192 210 100 108 110 124 126 124 126 162 102 104 100 In one or more embodiments, and as best illustrated in, the first inner edgeof the first phasing plugand the second inner edgeof the second phasing plugare adjacent to each other such that the first acoustic pathwayand the second acoustic pathwayconverge, such as at the central bore. Accordingly, in operation, acoustic signals from the first plurality of aperturesradiate inward along the first acoustic pathwayand acoustic signals from the second plurality of aperturesradiate inward along the second acoustic pathwayand merge at the central bore, then radiate through the hollow conduitof the front adapterto the circular exitof the dual compression driver. The overall acoustical cross-sectional area of the air paths, including the first and second plurality of apertures,, the first and second plurality of radial channels,, the first and second acoustic pathways,, the central bore, and the hollow conduitgradually increase to provide a smooth transition of acoustic signals through the dual compression driver. The disclosed configuration of the first and second annular diaphragms,and the first and second phasing plugs,decrease the path length between the radial exits of the first and second phasing plugs,to allow smooth merging of acoustic signals, and the use of a shared magnetbetween the first driver assemblyand the second driver assemblysignificantly decreases cost without sacrificing performance of the dual compression driver.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.